Why is there no string.Format Extension Method?

Why is there no built-in extension method like this?

public static string FormatOutput(this string format, params object[] args)
    return string.Format(format, args);

Now the following code

var output = string.Format("This guy's name is {0}", person.Name);

becomes this

var output = "This guy's name is {0}".FormatOutput(person.Name);

Which is much neater in my opinion.  Unfortunately we can’t name it ‘Format’ since the compiler gets confused between our extension method and the static method on the string class.